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Use of Stable Isotopes in Benthic Organic Material as a Baseline for Estimating Fish Trophic Positions in Lakes.

ABSTRACT: Estimating the trophic position of predators in food webs using stable isotopes requires establishing a 'baseline'; typically served by bivalves or snails. However, the frequent absence of such organisms in lakes leaves researchers in a difficult situation. Here we test the hypothesis that trophic position (TP) of largemouth bass (LB) in lakes can be estimated from δ¹⁵N of benthic organic material (BOM) in littoral surficial sediment. δ¹⁵N_LB as a function of δ¹⁵N_BOM was significant across 51 lakes with an R² of 0.84, supporting our hypothesis. In a subset of six lakes, the mean TP_LB did not differ significantly when calculated using baselines of δ¹⁵N in BOM, mussels (UN), gastropods (SN), or from a stable isotope mixing model. In a subset of 26 lakes, mean TP_LB calculated from δ¹⁵N_BOM and δ¹⁵N_UN baselines were not significantly different, but TP_LB calculated using δ¹⁵N_BOM was not significantly correlated with TP_LB calculated using δ¹⁵N_UN. Although δ¹⁵N_BOM should not be used interchangeably with δ¹⁵N_UN as a baseline for estimating TP_LB, δ¹⁵N_BOM can be useful as a separate baseline where estimates of fish TP are needed in all study lakes given that mussels are frequently absent and BOM is always available for collection.

SUBMITTER: Lake JL

PROVIDER: S-EPMC7751643 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Use of Stable Isotopes in Benthic Organic Material as a Baseline for Estimating Fish Trophic Positions in Lakes.

Lake James L JL Serbst Jonathan R JR Kuhn Anne A Smucker Nathan J NJ Edwards Phillip P Libby Alan A Charpentier Michael M Miller Kenneth K

Canadian journal of fisheries and aquatic sciences. Journal canadien des sciences halieutiques et aquatiques 20190701 7

Estimating the trophic position of predators in food webs using stable isotopes requires establishing a 'baseline'; typically served by bivalves or snails. However, the frequent absence of such organisms in lakes leaves researchers in a difficult situation. Here we test the hypothesis that trophic position (TP) of largemouth bass (LB) in lakes can be estimated from δ15N of benthic organic material (BOM) in littoral surficial sediment. δ15NLB as a function of δ<su ...[more]

PMID: 33353994

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Project description:The idea that interspecific variation in trophic morphology among closely related species effectively permits resource partitioning has driven research on ecological radiation since Darwin first described variation in beak morphology among Geospiza. Marine turtles comprise an ecological radiation in which interspecific differences in trophic morphology have similarly been implicated as a pathway to ecopartition the marine realm, in both extant and extinct species. Because marine turtles are charismatic flagship species of conservation concern, their trophic ecology has been studied intensively using stable isotope analyses to gain insights into habitat use and diet, principally to inform conservation management. This legion of studies provides an unparalleled opportunity to examine ecological partitioning across numerous hierarchical levels that heretofore has not been applied to any other ecological radiation. Our contribution aims to provide a quantitative analysis of interspecific variation and a comprehensive review of intraspecific variation in trophic ecology across different hierarchical levels marshalling insights about realised trophic ecology derived from stable isotopes. We reviewed 113 stable isotope studies, mostly involving single species, and conducted a meta-analysis of data from adults to elucidate differences in trophic ecology among species. Our study reveals a more intricate hierarchy of ecopartitioning by marine turtles than previously recognised based on trophic morphology and dietary analyses. We found strong statistical support for interspecific partitioning, as well as a continuum of intraspecific trophic sub-specialisation in most species across several hierarchical levels. This ubiquity of trophic specialisation across many hierarchical levels exposes a far more complex view of trophic ecology and resource-axis exploitation than suggested by species diversity alone. Not only do species segregate along many widely understood axes such as body size, macrohabitat, and trophic morphology but the general pattern revealed by isotopic studies is one of microhabitat segregation and variation in foraging behaviour within species, within populations, and among individuals. These findings are highly relevant to conservation management because they imply ecological non-exchangeability, which introduces a new dimension beyond that of genetic stocks which drives current conservation planning. Perhaps the most remarkable finding from our data synthesis is that four of six marine turtle species forage across several trophic levels. This pattern is unlike that seen in other large marine predators, which forage at a single trophic level according to stable isotopes. This finding affirms suggestions that marine turtles are robust sentinels of ocean health and likely stabilise marine food webs. This insight has broader significance for studies of marine food webs and trophic ecology of large marine predators. Beyond insights concerning marine turtle ecology and conservation, our findings also have broader implications for the study of ecological radiations. Particularly, the unrecognised complexity of ecopartitioning beyond that predicted by trophic morphology suggests that this dominant approach in adaptive radiation research likely underestimates the degree of resource overlap and that interspecific disparities in trophic morphology may often over-predict the degree of realised ecopartitioning. Hence, our findings suggest that stable isotopes can profitably be applied to study other ecological radiations and may reveal trophic variation beyond that reflected by trophic morphology.

Dataset Information

Use of Stable Isotopes in Benthic Organic Material as a Baseline for Estimating Fish Trophic Positions in Lakes.

Publications

Use of Stable Isotopes in Benthic Organic Material as a Baseline for Estimating Fish Trophic Positions in Lakes.

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